Icefall Ruins

Icefall Ruins enters the battlefield tapped.
During each of your upkeeps, remove an ice counter from all cards you own in exile. When the last is removed from a card, you may cast it from exile, and you may pay {0} rather than paying its mana cost.
{t}: Add {u} to your mana pool.
{2}{u}{u}, {t}, Exile a nonland card from your hand: Put three ice counters on it.